What Is Bus Filter Framework?

Bus Filter Framework, or BFF for short, is a static library that integrates with a KMDF-based upper filter driver into a bus filter driver.

The KMDF-based upper filter driver to be integrated provides for initialization of BFF necessary parameters for creation of bus filter device objects, optional handlers for PnP minor functions it wants to filter, and optional callback functions for creation and removal of bus filter device objects. With these handlers and callback functions, the upper filter driver may be transformed into a bus filter driver.

After initialization, BFF requires the upper filter driver to register a callback function with KMDF to preprocess IRP_MN_QUERY_DEVICE_RELATIONS, specifically for BusRelations. The callback function to be registered can be provided either by BFF or by the upper filter driver. In the latter case, that callback function must eventually call the one provided by BFF.

Additionally, BFF requires the upper filter driver to allocate context space for upper filter device objects on behalf of BFF. With that context space, BFF may manage creation and removal of bus filter device objects.

In summary, BFF is a framework for KMDF-based upper filter drivers to behave as bus filters. You don't need to write WDM drivers any more!